You really don't need the contraption, just a monitor stand (you can make one out of two bits of wood) or a nearby wall. Also a wireless keyboard (I use the Microsoft Multimedia Keyboard). I used to just use a laptop and when I travel I still do. In both cases I either rest them on my chest or (more often) suspend them in front of me and control them with my fingers and palms.
I'm healthy physically, I just prefer this. I swim, jog, cycle, do weights (I can lift my own body weight (120kgs, 6'1") with my arms vertically and horizontally, pushing and pulling).
The idea you get body sores or other negative effects is ridiculous. You need a good firm surface to look after your back posture, but obviously I'm always moving around, getting up and doing things. I don't wash myself with a rag on a stick.